Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Technologies related to the chirality of materials started from the days of Pasteur's separation of single enantiomers using tweezers. Since then, automated systems and chiral catalysts have been developed to detect chiral properties of materials, separate enantiomers, and obtain end product with single handedness. Many modern drugs are synthesized from single isomers. Detrimental or inactive mirror images of certain molecules can be identified at an early stage in the development process.
The U.S. market for chiral compounds has an annual growth rate of 8.8%, and is expected to exceed $1.8 billion in the next few years. Due to their importance in pharmaceutical industries, methods of chiral detection and chiral detectors have received significant attention.
Much success has resulted from improvements in chiral analysis techniques using existing polarimetric principles. More specifically, efforts have been made in the area of reducing noise associated with the measurements of the additional optical rotation induced by a chiral sample. Electronic or optical filters are often used to reduce the noise. Dual-beam methods have been developed, for example through comparison with a reference cell, mixing out-of-phase sinusoidal signals, switching between a signal and a reference beam, or using a two-frequency laser source with two orthogonal linearly-polarized waves. These methods may be used to determine the displacement from the null point of optical transmission.
Pockets cell modulation is also used for differential chiral analysis in flow cells. Alternating irradiation of linearly-polarized and circularly-polarized lights is carried out. The method is capable of handling systems in which there is a kinetic development of an enantiomeric component. There also have been some improvements in chiral detectors related to an improved sample-cell-based system for non-contact, rapid, low-noise, and accurate screening of chiral samples.
One alternative solution is using chiral columns in which the stationary phase is maintained chiral. Another approach uses proteomic basis of chiral drug action. Alternatively, two-photon polarization second-harmonic generation (SHG) spectroscopy can be employed. The SHG method provides a label-free platform to study bio-molecular interactions, such as the interaction between melletin and bio-membranes.
The chirality and molecular recognition of biological molecules are thus becoming prerequisites for many types of assemblies. For these assemblies the receptors are playing a key role in molecular recognition. Thus, chirality is emerging as an essential criterion for life, as many macromolecules including protein, DNA, and various metabolites etc., are chiral in nature.
The chirality in nanotechnologies is also important in practical applications such as functional self assembly, enantioselective catalysis, separation, biosensing, and optical devices. Given the predominant molecular nature of chirality, its implementation at the nanoscale relies upon successful transfer of chirality of template materials into nano-building blocks, e.g., ligand chirality in the case of nanoparticles (NPs). There are many biological systems at microscopic and macroscopic levels which are enriched by chiral objects such as proteins, nucleic acids, carbohydrates, amino acids, and nucleotides.